The present invention relates to gas pressure regulators and more particularly to regulators for regulating pressure in large volume, highly dynamic flows of gas.
One of the technical challenges facing the natural gas vehicle (NGV) industry, and other pressurised gas using devices, is the need for an accurate, reliable pressure regulator to supply gas to the system. Currently, mechanical (analogue) regulators are being used that have inherent errors due to dynamic droop, hysteresis, and supply-pressure effects. These are single-stage or two-stage designs that use either a diaphragm or a piston coupled to a valve to control pressure. Durability has been a problem with a number of regulators. Some regulators have been prone to failures of the valve-seat, diaphragm, and o-rings. Others have been reported to jam or stick in the open position, or resonate (squawking, honking).
To address these concerns an electronic regulator has been developed that is controlled by a proportional-integral-derivative (PID) controller. This regulator is described in U.S. Pat. No. 6,003,543, filed Jun. 11, 1997, the disclosure of which is incorporated herein by reference. The regulator includes a high-speed solenoid valve, a pressure sensor, and an electronic control unit. This regulator can significantly improve the accuracy of the injector supply pressure by reducing droop (steady-state error), hysteresis, and the error due to changes in storage tank pressure. However, this system at present can only meet the fuel flow requirements of smaller engines.
U.S. Pat. No. 3,455,323 to Haupt, provides a gas regulator using electronic pressure control. The regulator includes a housing having an inlet, an outlet and a regulator valve for controlling flow through the housing from the inlet to the outlet. A pressure responsive member supported in a control chamber within the housing controls displacement of the regulator valve. The control of pressure in the control chamber however requires multiple valves each having a solenoid to control the bleeding and feeding of the control pressure in the control chamber therethrough. The arrangement of valves and solenoids is complex to assemble upon manufacture and requires awkward manipulation in use. Furthermore, the valves are arranged to be vented to the atmosphere when bleeding gas from the control chamber which is undesirable when the gas to be regulated involves fuels and the like which are typically not friendly to the environment.
British Patent Application 2 121 563 provides a pressure regulating apparatus for gaseous and liquid flow media. The apparatus includes a housing having an inlet, an outlet and a regulator valve controlled by a pressure responsive member mounted in a control chamber similarly to the above noted U.S. patent to Haupt. Control of the pressure in the control chamber however requires a complex arrangement of ports and valves for selectively feeding or bleeding the control chamber on both sides of the pressure responsive member. Furthermore, bleeding of the control chamber on both sides of the pressure responsive member requires venting externally of the housing. This is undesirable as noted above when regulating pressure of fuels and the like which should not be vented to the atmosphere.
The present invention is concerned with certain improvements to gas regulators for large volume, highly dynamic flows of gas which address some of the deficiencies of the above noted prior art.
According to one aspect of the present invention there is provided a gas pressure regulator for regulating the pressure of a gas flowing from a source of the gas under pressure to a device for using the gas, the regulator comprising:
a regulator housing having a gas inlet for receiving the gas and a gas outlet for the delivery of the gas from the housing;
a pressure reducing valve in the housing for controlling the flow of gas from the inlet to the outlet;
a pressure reducing valve controller comprising:
a control chamber;
a feed valve having an inlet for receiving gas from said source of gas under pressure and a control pressure outlet coupled to the control chamber, the feed valve having an open state in which the valve is fully open and a closed state in which the valve is fully closed;
a bleed valve having an inlet coupled to the control chamber and an outlet coupled to the gas outlet of the regulator housing, the bleed valve having open state in which the valve is fully open and a closed state in which the valve is fully closed;
a high speed solenoid valve actuator for operating the feed and bleed valves;
a pressure responsive member in the control chamber and coupled to the pressure reducing valve for movement therewith, the pressure responsive member being movable in response to variations in a control pressure in the control chamber;
a pressure monitor for monitoring an actual gas pressure at the gas outlet of the regulator housing;
a controller coupled to the pressure monitor and to the solenoid valve actuator for controlling operation of the feed and bleed valves between their respective closed and open states to produce a desired gas pressure at the gas outlet of the regulator housing.
The regulator of the present invention provides an effective means of regulating pressure of large volume, highly dynamic flows of gas using a pressure reducing valve which is simple in design and use. The arrangement of the bleed valve is particularly useful for ensuring that gaseous fuels being regulated are not vented to the atmosphere, but rather are vented to the outlet of the regulator where the fuel can be subsequently consumed with the pressure regulated gaseous fuel exiting the regulator.
This regulator is of the piston or diaphragm type, with the pressure responsive member, e.g. piston or diaphragm, moving in response to a pressure difference across the member, and controlling the pressure reducing valve. In this case, the control pressure is supplied by the gas being regulated, under the control of feed and bleed valves. This allows the rapid regulation of the supply pressure with a limited energy input. The back pressure is the outlet pressure.
To adjust the regulator in response to a reduced gas or fuel demand, the control chamber pressure must be reduced using the bleed valve. Because the control gas may be gaseous fuel, it is not acceptable to bleed this gas into the atmosphere, so that the gas used for control is bled from the control chamber into the gas outlet of the regulator housing to be used as fuel.
The use of a high speed solenoid actuator for the feed and bleed valves allows the same kind of dynamic control of the control pressure that can be achieved with the pressure control system disclosed in prior U.S. Pat. No. 6,003,543, referred to above, but for much larger flow rates.
The solenoid valve actuator may be a single solenoid coil opening and closing the feed and bleed valves in opposition. Pulse width modulation and/or frequency modulation may be used to vary the ratio of open and closed times and thus the pressure in the control chamber. Alternatively, two coils may be used for the two valves. This allows independent control of the valves to compensate for inertial effects, for example pressure spikes or time lags in flow changes, in response to rapid changes in flow demand.
The desired gas pressure at the gas outlet is preferably a set point pressure. The controller thus preferably comprises a mechanism for controllably varying the set point pressure.
The controller preferably includes a signal generating mechanism for delivering a pulsed electrical signal for operating the feed and bleed valves and a signal varying mechanism for controllably varying the pulse width of the electrical signal.
The high speed solenoid valve actuator preferably includes a pressure reducing valve closing mechanism for closing the pressure reducing valve in response to deactivation of the high speed solenoid valve actuator. This arrangement provides a positive shut-off for ensuring no gaseous fuel is released from the regulator in the event of a failure or loss of power to the solenoid valve actuator.
In a preferred embodiment, the feed and bleed valves are coupled for movement together between a bleed position in which the bleed valve is in the open state and the feed valve is in the closed state and a feed position in which the feed valve is in the open state and the bleed valve is in the closed state. The high speed solenoid valve actuator would thus preferably comprise a single solenoid coupled to the feed and bleed valves with the feed and bleed valves being positioned in the bleed position upon deactivation of the single solenoid.
The feed and bleed valves are preferably both coupled to communicate with the control chamber on a first side of the pressure responsive member. A port may then be provided coupling the control chamber on a second side of the pressure responsive member to the gas outlet of the regulator housing such that back pressure on the second side of the pressure responsive member is substantially equal to the actual gas pressure at the gas outlet. A biasing mechanism may additionally be provided on the second side of the pressure responsive member acting in a direction corresponding to closing the pressure reducing valve.
There may be provided a shut-off valve coupled to the gas inlet of the regulator housing. When closed, the shut-off valve ensures that the gaseous fuel is not leaked through the regulator housing when the device using the pressure regulated gas is not intended to be used.
The shut-off valve may include a solenoid operating mechanism for displacing the valve between respective open and closed positions. The solenoid operating mechanism is preferably arranged to be oriented in the closed position when de-energised to ensure that it operates as it is intended, for closing the flow of gaseous fuel in the event of a power loss or failure. The shut-off valve is preferably arranged to be closed in response to a shut-off condition sensed by the pressure monitor which may include a signal from the device using the gas that it is being shut-off or a signal from the controller indicating a failure.
According to a second aspect of the present invention there is provided in combination:
a supply of pressurised gas;
a gas using device for using the gas; and
a gas pressure regulator coupled to the gas using device and the supply of pressurised gas for controlling the pressure of gas delivered from the supply to the gas using device, said pressure regulator comprising:
a regulator housing having a gas inlet for receiving the gas and a gas outlet for the delivery of the gas from the housing;
a pressure reducing valve in the housing for controlling the flow of gas from the inlet to the outlet;
a pressure reducing valve controller comprising:
a control chamber;
a feed valve having an inlet for receiving gas from said source of gas under pressure and a control pressure outlet coupled to the control chamber, the feed valve having an open state in which the valve is fully open and a closed state in which the valve is fully closed;
a bleed valve having an inlet coupled to the control chamber and an outlet coupled to the gas outlet of the regulator housing, the bleed valve having open state in which the valve is fully open and a closed state in which the valve is fully closed;
a high speed solenoid valve actuator for operating the feed and bleed valves;
a pressure responsive member in the control chamber and coupled to the pressure reducing valve for movement therewith, the pressure responsive member being movable in response to variations in a control pressure in the control chamber;
a pressure monitor for monitoring an actual gas pressure at the gas outlet of the regulator housing;
a controller coupled to the pressure monitor and to the solenoid valve actuator for controlling operation of the feed and bleed valves between their respective closed and open states to produce a desired gas pressure at the gas outlet of the regulator housing.
In a gas using system, when the supply of pressurised gas is mounted remotely from the gas using device, coupled by a gas line, the gas pressure regulator is preferably mounted adjacent the supply of pressurised gas. The pressure monitor is then preferably coupled to the gas line adjacent the gas using device so that the gas line coupling the supply to the gas using device is at the regulated pressure instead of the much greater supply pressure. This is particularly useful in a gaseous fuelled vehicle wherein the fuel lines coupling the pressurised gaseous fuel tank to the engine can be maintained at the regulated pressure instead of the supply pressure of the fuel tank while still being able to accommodate the varying pressure requirements of fuel to be delivered to the engine.
The regulator according to the present invention may be incorporated into various gaseous fuelled devices or gas consuming systems, including the following:
1) as a stand alone regulator coupled within the gas line at any location between a supply and a gas using device;
2) as a regulator integrated with a tank valve and a tank solenoid to produce one component;
3) as a regulator for vehicles with gaseous fuelled combustion engines including natural gas fuelled vehicles (NGVs) and the like; and
4) as a regulator for vehicles with fuel cell powered engines for regulating fuel supplied to the fuel cell of the vehicle.
According to a further aspect according to the present invention there is provided a method of regulating pressure of a gas flowing from a source under pressure to a device for using the gas, the method comprising:
providing a regulator housing having a gas inlet, a gas outlet and a pressure reducing valve for controlling the flow of gas from the inlet to the outlet;
connecting the gas inlet in communication with the source under pressure;
connecting the gas outlet in communication the device for using the gas;
providing a pressure reducing valve controller having a control chamber, a feed valve and a bleed valve, each of the feed and bleed valves having an open state in which the valve is fully open and a closed state in which the valve is fully closed;
connecting the feed valve to the source under pressure at an inlet of the feed valve and to the control chamber at an outlet of the feed valve;
connecting the bleed valve to the control chamber at an inlet of the bleed valve and to the gas outlet of the regulator housing at an outlet of the bleed valve;
providing a pressure responsive member in the control chamber;
coupling the pressure responsive member to the pressure reducing valve for movement therewith in response to variations in control pressure in the control chamber;
monitoring an actual gas pressure at the gas outlet of the regulator housing; and
controlling, in response to the actual gas pressure monitored, operation of the feed and bleed valves between their respective closed and open states to produce a desired gas pressure at the gas outlet of the regulator housing.
The operation of controlling the bleed valve preferably includes venting the control chamber to the gas outlet of the regulator housing.
The control pressure in the control chamber is preferably maintained substantially greater than the actual gas pressure at the gas outlet of the regulator housing.
While the invention has been developed with a view to its application in gaseous fuelled vehicles, electronic regulators can also be used as stand-alone regulators in other applications.